A commercial diagnostic ultrasound scanner (Octoson) was modified for performing hyperthermia treatments. The temperature elevations were induced in tissues by four large, focused ultrasonic transducers whose common focal zone was scanned along a computer controlled path as determined from B-scan images. The system is described and the results of preliminary tests demonstrating some of its capabilities are given. Extensive tests with canine thighs and kidneys were performed. The blood flow to the kidneys was controllable, and thus tumours having different blood perfusion rates could be simulated. The results showed that the system is capable of inducing a local temperature maximum deep in tissues (up to 10 cm was tested) and that tissues with high perfusion rates could be heated.

In this study a scanned focused ultrasound (SFUS) system was used to heat 66 tumours at various anatomical locations in 52 patients. A total of 160 treatments were given. On average, temperatures were measured in 14 or 15 locations in the scanned volume. The time-averaged temperatures over the 30 min treatment period in the best treatment of each tumour were 44.0 +/- 2.4 degrees C (mean +/- SD) and 39.6 +/- 1.5 degrees C at the location of the highest and lowest sensor, respectively. On average, 39% of the sensors were above 42.5 degrees C. When only the cases that were judged to be good candidates for the hyperthermia device were analysed, 64% of the sensors reached a temperature over 42.5 degrees C with the highest temperature achieved being 45.9 +/- 2.3 degrees C and the lowest 40.7 +/- 1.4 degrees C. Although the system tested has many technical limitations (for example, fixed frequency, beam geometry and power during the scan cycle), the results demonstrate that therapeutic temperatures can be achieved in many tumours. Significantly better temperatures are expected when all of the theoretical potential of scanned focused ultrasound systems has been used.

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A commercial diagnostic ultrasound scanner (Octoson) was modified for performing hyperthermia treatments. The temperature elevations were induced in tissues by four large, focused ultrasonic transducers whose common focal zone was scanned along a computer controlled path as determined from B-scan images. The system is described and the results of preliminary tests demonstrating some of its capabilities are given. Extensive tests with canine thighs and kidneys were performed. The blood flow to the kidneys was controllable, and thus tumours having different blood perfusion rates could be simulated. The results showed that the system is capable of inducing a local temperature maximum deep in tissues (up to 10 cm was tested) and that tissues with high perfusion rates could be heated.